1. Field of the Invention
The present invention relates to receivers for digital broadcasting.
2. Description of the Related Art
In Europe, Digital Audio Broadcasting (DAB, registered trademark) has been performed as digital sound broadcasting according to a European Research Coordinating Agency (Eureka) 147 specification. In DAB, various encoding processes are applied to a plurality of digital data items to convert them finally to an orthogonal-frequency-division-multiplex (OFDM) signal, and a main carrier signal is differential-quadrature-phase-shift-keying (D-QPSK) modulated by the OFDM signal to form a transmission signal. Digital audio data and other digital data of up to 64 channels can be broadcasted at the same time.
FIG. 3 shows the structure of the OFDM signal in the time domain. The OFDM signal is formed of a plurality of frames. Each frame is formed of (m+1) symbols. DAB has four transmission mode. In mode II, for example, the time length of a frame is 24 ms and the number (m+1) of symbols is 76.
Each frame is divided into a synchronizing channel SC, a fast information channel FIC, and a main service channel MSC, with symbols being used as units. The synchronizing channel SC is used for processing, such as frame synchronization and automatic frequency control (AFC), in receivers. The synchronizing channel SC is formed of two symbols, the first symbol thereof is a null symbol NULL, and the second symbol thereof is a symbol TFPR used for phase reference.
The fast information channel FIC is used for providing data related to the main service channel MSC, and includes data, such as the time, the date, a type, a data arrangement, and traffic and message control data. The main service channel MSC includes digital audio data and various digital data items serving as main data.
DAB receivers need to perform signal processing, such as orthogonal demodulation, fast Fourier transform (FFT), OFDM demodulation, deinterleaving, error correction, and digital-to-analog (D/A) conversion, in response to signal processing performed at a transmitting side. Some of these signal processing items are executed in general by a digital signal processor (DSP). The DSP is always in an operating state while DAB is being received, and does not enter a sleep state (idle state).
The present invention has been made in consideration of the following condition. It is an object of the present invention to allow the DSP for processing digital sound broadcasting (DSB) data to enter a sleep state to reduce power consumption.
The foregoing object is achieved in one aspect of the present invention through the provision of a receiving apparatus for receiving a signal having a plurality of types of data in each frame period, including a plurality of accumulation means for accumulating the plurality of types of data, respectively, in each frame period; at least one calculation-processing means for processing each of the plurality of types of data accumulated by the plurality of accumulation means; and storage means for storing information indicating that each of the plurality of types of data has been accumulated into accumulation means, wherein the calculation-processing means applies processing to data accumulated into accumulation means, corresponding to information indicating the completion of data accumulation stored in the storage means.
In the receiving apparatus, since calculation processing starts with data which has been accumulated among the plurality of types of data, each processing is sequentially performed from the beginning of a frame period, a period is formed near the end point of the frame period, in which the calculation-processing means can enter, for example, a sleep mode.
The receiving apparatus may be configured such that the storage means further stores information indicating the order of priority in which processing is applied to each of the plurality of types of data, and the calculation-processing means applies processing to the plurality of types of data in the order of priority.
Therefore, when the calculation-processing means is ready to start processing, if two or more data items need to be processed, data processing is performed in an appropriate order according to the order of priority.
The receiving apparatus may be configured such that the storage means further stores information indicating the completion of processing applied to each of the plurality of types of data, and the calculation-processing means enters a sleep state when all processing applied to the plurality of types of data has been completed.
With this configuration, since it is positively checked that all processing applied to the data has been completed, before the calculation-processing means enters a sleep state in a sleep period formed near the end point of a frame period, the calculation-processing means enters the sleep state without any problems.
The receiving apparatus may be configured such that the storage means further stores information indicating that corresponding data is allowed to be processed, and the calculation-processing means applies processing to data for which data processing is allowed among the plurality of types of data.
With this configuration, processing which does not need to be performed in the frame period is positively omitted, or data processing which cannot be started can be postponed. Therefore, a sleep period can be formed near the end point of a frame period.
The foregoing object is achieved in another aspect of the present invention through the provision of a receiving apparatus for receiving a signal having a plurality of types of data in each frame period, including a plurality of accumulation means for accumulating the plurality of types of data, respectively, in each frame period; at least one calculation-processing means for processing each of the plurality of types of data accumulated by the plurality of accumulation means; and storage means for storing information indicating that each of the plurality of types of data has been processed; wherein the calculation-processing means enters a sleep state when all processing applied to the plurality of types of data has been completed, according to the information indicating the completion of processing.
The foregoing object is achieved in still another aspect of the present invention through the provision of a receiving apparatus for receiving a signal having a plurality of types of data in each frame period, including a plurality of accumulation means for accumulating the plurality of types of data, respectively, in each frame period; at least one calculation-processing means for processing each of the plurality of types of data accumulated by the plurality of accumulation means; and storage means for storing information indicating that each of the plurality of types of data is allowed to be processed; wherein the calculation-processing means applies processing to data accumulated into the accumulation means corresponding to the storage means for storing information indicating that data is allowed to be processed.
The foregoing object is achieved in yet another aspect of the present invention through the provision of a receiving apparatus for receiving a signal having a plurality of types of data in each frame period, including a plurality of accumulation means for accumulating the plurality of types of data, respectively, in each frame period; at least one calculation-processing means for processing each of the plurality of types of data accumulated by the plurality of accumulation means; and storage means for storing information indicating that each of the plurality of types of data is allowed to be processed, information indicating that each of the plurality of types of data has been accumulated into accumulation means, information indicating the order of priority given to each of the plurality of types of data, and information indicating the completion of processing applied to each of the plurality of types of data, wherein the calculation-processing means performs data processing in the order of priority given to each data when a plurality of data corresponding to information indicating that data processing is allowed has been accumulated into the accumulation means, and the calculation-processing means enters a sleep state when all processing applied to the plurality of data has been completed.